Problem: $ (-72\% \div 90\%) \div 20\% $
Convert each percentage into a decimal dividing by $100$ $ (-0.72 \div 0.9) \div 0.2 $ $ = -0.72 \div (0.9 \times 0.2)$ $ = -0.72 \div 0.18$ ${0}$ ${1}$ ${8}$ ${7}$ ${2}$ ${0}$ $\text{Shift the decimal 2 to the right.}$ ${7}$ $\text{How many times does }18\text{ go into }{7}\text{?}$ ${0}$ ${7}$ $-\vphantom{0}$ ${7}\div18={0}\text{ or }18\times{0} = {0}$ ${2}$ $\text{How many times does }18\text{ go into }{72}\text{?}$ ${4}$ ${7}$ ${2}$ ${0}$ $-\vphantom{0}$ ${72}\div18={4}\text{ or }18\times{4} = {72}$ ${0}$ $\text{How many times does }18\text{ go into }{0}\text{?}$ ${0}$ ${0}$ ${0}$ $-\vphantom{0}$ ${0}\div18={0}\text{ or }18\times{0} = {0}$ A negative number divided by a positive number is a negative number. $-0.72 \div 0.18 = -4$ Convert the decimal into a percentage by multiplying by $100$. $-4 = -400\%$